Aligned column headers to top for consistent rendering.

"vertical-align: bottom;", which is Bootstrap's default for <th>
elements, renders inconsistently when the cell contains enough content
to wrap.

Nuking the style lets ".table th, .table td" win with
"vertical-align: top;" and renders consistently.

Review: https://reviews.apache.org/r/14328/
Build against different SASL versions.

Review: https://reviews.apache.org/r/14358
Preserved exit status when SIGTERM is received.

Review: https://reviews.apache.org/r/14153
Fixed formatting log output in signal handler.

Review: https://reviews.apache.org/r/14375
Fixed slave's finalize() method to not throw segfault.

Review: https://reviews.apache.org/r/14098
Enabled the kernel OOM killer.

The Mesos userspace OOM handler does not conform to the practical
restrictions imposed upon it given the potential states the kernel can
be in when it gets the OOM notification. The result of this has been
numerous deadlocks because the Mesos OOM handler blocks on a lock that
is being held by the task it is trying to kill.

This patch does not try to fix the issues with the OOM handler. Instead,
it hands over the job of OOM-killing to the kernel. The end result is
very similar. The downside to this approach compared to the approach
it's moving away from is now when the Mesos OOM handler reads the
memory.stats they will be after the oom condition occurred. The "maximum
usage" is still captured but the breakdown is lost. This exposes another
weakness in the memcg implementation regarding page cache awareness.
However, the reliability improvements outweigh the weakness in stats.

From: David Mackey <tdmackey@booleanhaiku.com>
Review: https://reviews.apache.org/r/14024
Added memory threshold notifications for inducing OOMs.

Review: https://reviews.apache.org/r/14043
Updated the balloon tests to test the memory threshold.

Review: https://reviews.apache.org/r/14044
Added resource checks to slave recovery tests.

Re-submit of reverted resource checks in slave recovery,
see: https://reviews.apache.org/r/13764/

From: Ian Downes <ian.downes@gmail.com>
Review: https://reviews.apache.org/r/14002
Fixed a bug with resource accounting during slave removal.

Review: https://reviews.apache.org/r/14431
Fixed a bug with resource accounting in reconciliation.

Review: https://reviews.apache.org/r/14435
Added a task reconciliation test.

Review: https://reviews.apache.org/r/14436
Added a union operator to hashset.

Review: https://reviews.apache.org/r/14437
Re-structured the Slave::tasks map.

Review: https://reviews.apache.org/r/14438
Added a missing include.
Fixed ARG_MAX compilation issue on some POSIX systems.
Added slave recovery doc.
Fixed a case where Framework re-registration time was not being
updated.

Also refactored the time into an Option.

Review: https://reviews.apache.org/r/13744
Fixed an issue where the Master unnecessarily sends a "Framework
failed over" message when the scheduler driver retries an initial
failover re-registration.

Review: https://reviews.apache.org/r/13757
Fixed the slave to ignore messages not originating from the expected
master.

Review: https://reviews.apache.org/r/14541